<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta
      name="viewport"
      content="width=device-width, initial-scale=1.0"
    />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
    <style>
      div {
        width: 80px;
      }

      input[type='text'] {
        width: 50px;
        height: 44px;
        outline: none;
        border: 1px solid #ccc;
        text-align: center;
        border-right: 0;
      }

      input[type='button'] {
        height: 24px;
        width: 22px;
        cursor: pointer;
      }

      input {
        float: left;
        border: 1px solid #ccc;
      }
    </style>
  </head>

  <body>
    <div>
      <input type="text" id="total" value="1" readonly />
      <input type="button" value="+" id="add" />
      <input type="button" value="-" id="reduce" disabled />
    </div>
    <script>
      const total = document.getElementById('total')
      const add = document.getElementById('add')
      const reduce = document.getElementById('reduce')
      add.addEventListener('click',function(){
        total.value = ++total.value
        reduce.disabled = false
      })
      reduce.addEventListener('click',function(){
        let value = total.value
        --value==1?reduce.disabled = true:``
        total.value = value
      })
    </script>
  </body>
</html>
